I presently own a laptop as my primary just for portability but it drives me nuts how much more often I am replacing them than I would an actual desktop because I can upgrade a desktop to extend its life way more easily than my laptop.This is exactly it for me. I'm even picky re: laptops for this reason. My Microsoft Surface Pro just took a big dump and fixing it is like "Ehhhh"
All in Ones have places for tight spaces and some people just prefer them but they do have a rep of frying the fuck out of themselves.
All that junk compacted behind a monitor will get hot and shorten the life of the parts. Boards just love to warp like hell under those conditions.